why NOT to train to failure 
dg, sorry about creating a new thread [not trying to dispand yours], but for whatever reason my computer is being an arse... and it wont let me reply in the other thread.
yopu posted this in the other thread: [i put numbers to make it eaiser to read + understand my replies]
#1Its been proven. By body builders all over the world and by guys decades ago.
#2I always train to failure and in by no means small or skinny or weak...
I really dont get it.
#1 many HIT advocates [inc MM+dorian] would have you belive that they trained 1 or 2 sets to failure all the time. this is simply not true. and like johnny [rightly] says, all weightlifting theories will stimulate/provoke a reaction from your body, some are simply better than others.
#2 as above, it all works, but training to failure has wasted alot of the progress you could have made. look at the science* behind weightlifting to provoke hypertrophy as a response. *science is a nessecary evil i'm afarid, we'd all like to walk through life blind, but it doesn't work like that i'm afraid.
lets [for arguements sake] say both of us have a 3RM on the bench press of 100kg.
now, you train to failure, and i do not.
true HIT is one set to failure, some may do two or even three. for the purposes of this disscussion we will say you do 2 sets to failure[to ensure you get the 'benifits' of both extremes]. i am sure your are aware [not fully though, but it will become clear] of how important progressively increasing load [weight, intensity, lbage etc etc] is each session. this is called linear progression. something that is hard to moniter when training to failure, afetr all, if yo can do 7 reps one session, do you go for 8/9/10 this session, or up the weight and go till failure again??
your workout would look somewthing like this:
**1x7+1x6@80kg** = 13reps over 2sets = total volume of 1040kg
having gone to failure on each set.
**xxx**given that our 3RM=100kg, the likey hood of you getting those reps is slim anyway,i was just being generous, even so:
my workout is cycled up and down in both load and volume, and this week, looks like this: [sets cycled up from 6-9]
7x3@80kg = 21reps over 7sets = total volume of 1680kg
having gone no where near failure on any set.
in the 6x3week i get 1440kg, and in the 9x3 week i get 2160kg!!!!
so, you have [a] lifted less total reps, meaning less training stimulus. lifted less total volume, resulting in the same reduced training stimulus and [c] gone to total failure on each set, forcing your body to take severalk days longer to recover than mine. this translates to me doing more workouts per unit time [say, over a year i might get 10-20 sessions on you, upping the weight each time] and so, if i'm upping the weight faster, that means i'm getting stronger and or bigger, faster, and have more vital motor learning time.
so you see, by training to failure you are: decreasing the load, and decrasing the volume, and decrasing the frequency of your training. none of this will translate into better gains than my program above, or any multiple set, none failure program....